Pressure reduction check valve



J. F. HOFFER PRESSURE REDUCTION CHECK VALVE `lune 27, 1944.

Filed Jan. 2, 1942 fnf/259.5.

Patented June 27, 1944 PRESSURE REDUCTION CHECK VALVE James F. Hofler,Detroit, Mich., assignor toI Ex- Cell-O Corporation, Detroit, Mich., acorporation of Michigan Application January 2, 1942, Serial No. 425,396

Claims.

The present invention relates to a novel pressure reduction check valveadapted for use with jerk-type fuel injection pumps.

In fuel injection systems embodying jerk-type pumps, the pump isconnected through an outlet check valve to a supply tube leading to theinjection nozzle. In certain check valves heretofore employed, the valvemember is arranged to displace a xed volume of fuel toward the nozzlebefore fully opening the flow passage between the pump and the supplytube. On closing, the valve member displaces the same volume of fluid inthe reverse direction toward the pump. The purpose of this fluiddisplacement toward the pump is to reduce the pressure in the supplytube and the nozzle passages so as to effect rapid closing of the nozzleat the end of each normal injection period, and to preventafter-injection and nozzle leakage during the comparatively longintervals between the normal injection periods. Such retracting typecheck valve, however, has the disadvantage that it Vtends to result inpartial cavitation of the injection system at the outlet side of thevalve.

One of the objects of the present invention is to provide a new andimproved check valve of the pressure reduction type rather than of theretraction type, whereby to obtain all of the advantages while avoidingthe disadvantages of the latter type.

A further object is to provide a novel check valve which is operable toreduce the residual pressure as desired in the injection or supply tubewithout resulting in cavitation under any condition of operation.

Another object is to provide a novel pressure reduction check valve ofthe foregoing character which is simple and inexpensive in construction,and which is efficient and reliable in operation.

Further objects and advantages will become apparent as the descriptionproceeds.

In the accompanying drawing, Figure 1 is an enlarged fragmentary axialsectional View of a check valve embodying the features of my invention.

Fig. 2 is a fragmentary transverse sectional View taken along line 2-2of Fig. 1.

While the invention is susceptible of various modifications andalternative constructions, I'

have shown in the drawing and will herein describe in detail thepreferred embodiment, but it is to. be understood that I do not therebyintend to limit the invention to the specic form disclosed, but intendto cover all modifications and alternative constructions falling Withinthe spirit and scope of the invention as expressed in the appendedclaims.

Referring more particularly to the drawing, the check valve is adaptedfor use with a jerktype fuel pump in a fuel injection system. The

pump per se forms no part of the present invention and, hence, is notdisclosed in detail. It is sufcient to say that the pump comprises abody I having a cylinder 2 with a fuel discharge passage 3. A piston 4is reciprocable in the cylinder 2, and is operable on each workingstroke todisplace a charge of fuel under pressure to the passage 3.

The check valve, which is indicated generally at 5, is suitably mountedon the pump body I to connect the pump discharge passage 3 With a supplytube (iy leading to an injection nozzle (not shown). In its preferredform, the check valve 5 comprises a stationary Valve body 'I vhaving avalve passage 8 formed in its outer Vend with an annular valve seat l9,and a reciprocable plunger I Il having a valve member II on its innerend adapted for engagement with the seat. A coiled compression spring I2tends to hold the Valve member II against the seat 9 with apredetermined pressure. The different elements of the valve 5 areconfined in assembled relation, and the Valve body 1 is secured within abore I3 in the pump body I by means of a suitable retainer I4.

The valve body 1 consists of a sleeve or housing I5 having an axial boreI6, and formed on its inner end with an enlarged circular head I1 seatedagainst a gasket I8 in the inner end of the bore I3. The valve passage 8opens from the'loore I6 coaxially `through the head I 'I forcommunication with the pump discharge passage 3. To secure the valvebody 'I tightly in position, a clamp sleeve I9 on one end of theretainer I4 is threaded into the outer end of the bore I3 and into endengagement with the head I1.

The clamp sleeve I9 has a large axial bore 20 which loosely receives thesleeve I5 of the valve body 'I and coacts therewith to dei-lne anintermediate annular flow passage 2l The inner end of the bore 20 opensaxially to a bore or passage 22 formed with a counterbore 23constituting the fuel outlet from the valve 5.

The valve bore I6 within the sleeve I5 is formed in the outer end with arelatively large counterbore 24. Accurately machined pilot guides 25 and26 of slightly reduced diameters are formed respectively .adjacent theinner end of the bore I6,and in the outer end of the counterbore 24.

The valve plunger l extends reciprocably in the bore I6, and is providedadjacent the inner end with a relatively small piston 21 disposed withinthe guide 25, and at its outer end with a relatively large piston 28disposed within the guide 26. Predetermined peripheral clearances 29 and38, selected to give the desired operating characteristics, are providedbetween the pistons 21 and 28 and their respective guides 25 and 26. Thevalve member I is smaller in diameter than the inner end of the bore I6to provide an annular passage 3| open to the valve seat 9. This passage3| opens through radial ports 32 in the sleeve I to the iloW passage 2|.It Will be seen that when the valve member is lifted from the seat 9,fuel will flow from the pump cylinder 2 through the discharge passage 3,the seat 9, the passage 3|, the ports 32, and the passage 2| to theouter end of the bore 28, and then through the counterbore 23 and bore22 to the conduit 6.

The valve closing spring I2 seats at one end against a shoulder 33 atthe end of the counterbore 23, and at the other endagainst a shoulder 34in the piston 28. It will be evident that the valve plunger l0 is of thediiferential type with the piston 28 dening a relatively large pressurearea, and the piston 21 dening a relatively small pressure area. Theintermediate portion of the bore I6 between the collars 21 and 28constitutes a dashpot chamber 35 having inlet and egress orices dened bythe selected clearances 29 and 30.

To provide suitable means for connecting the passage 22 with thepressure tube 6, the retainer I4 is formed with a sleeve 36 having aninternally threaded bore 31 open to the passage 22 and a beveled orconical outer end face 38. A bolt 39 is threaded into the bore 31, andhas a head 48 with a conical face 4| in opposed relation to the face 38.The bolt 39 extends through a bore 42 in a coupling member 43 adapted tobe clamped between the sleeve 36 and the head 48. Opposite ends of thebore 42 are formed With conical faces 44 and 45 complemental to andadapted for fluid-tight engagement respectively With the faces 38 and 4|when the bolt 39 is tightened.

The bolt 39 is formed with an axial bore 46 open at the inner end tothepassage 22, and opening at the other end through radial ports 41 to thebore 42. An annulargroove 48 in the bore 42 is connected through a port49 to the interior of a tubular projection '58 on the coupling member 43in which the pressure tube 6 is tightly secured.

In operation, the spring |2 normally seats the valve 5 with a forcedetermining the desired valve opening pressure. When this pressure isattained during the working stroke of the pump piston 4, the valve 5will open, and fuel will be supplied at a high injection pressure to thenozzle. In the return stroke of the piston 4, the pressure will drop toterminate the injection period. To dissipate or reduce the storedpressure energy in the injection line at the end of each injectionperiod, the closing of the valve 5 is retarded so as to permit thereturn flow or escape of a small volume of fuel past the valve seat 9into the pump cylinder 2 before the valve is fully closed. This isaccomplished by a dashpot action. During outward movement of the valveplunger I8, the dashpot chamber 35 is filled with fuel entering throughthe clearances 29 and 36. During closing movement, the spring '|2 actson the plunger l0 to maintain the fuel in the chamber 35 underconsiderable pressure, and the magnitude of this pressure is determinedby the ratio of the differential areas of the collars 21 and 28.Consequently, the valve 5 will close at a rate deter-- mined by theescape of fuel from the chamber 35 through the clearances or orifices 29and 3|).

The valve 5 lends itself, through selective dmensioning, to control ofthe closing period in accordance with the operating characteristicsdesired. The pressure of injection, and hence the stored pressure energyin the system at the end of injection will increase upon an increase inthe rate or quantity of injection due to the compressibility of thefuel. Usually, the valve closing period is determined to relieve themaximum stored pressure energy that is attained over the operatingrange.

By selective proportioning of the maximum valve lift, the spring rate,the valve seat diameter, and the restrictive flow area of the orifices29 and 38, the degree of valve lift can be caused to vary with the rateand quantity of injection from minimum to maximum, so as to vary correspondingly the duration of the valve closing period.

Ordinarily, the pressure in the dashpot chamber 35 is induced only bythe action of the spring |2. However, the force tending to close thevalve can be increased by restricting the flow area of the passage 2| soas to cause a pressure drop therethrough. In this event, 'the ilow areaof the orifice 29 preferably is held to a minimum, while that of theorifice 30 is suitably increased. During the valve closing movement, thepressure acting on the area of the collar 28 will then be higher thanthe opposing pressure acting on the area of the collar 21, thusincreasing the pressure in the dashpot chamber 35. As a result, theresidual pressure in the line is caused to vary directly in accordancewith the rate and quantity of injection.

It will be evident that I have provided a valve of the pressurereduction type which serves to prevent the trapping of highly compressedfluid in the injection line simply by delaying slightly the closing ofthe valve. By relieving the residuual pressure after injection,the'nozzle will close quickly, and the after-injection and the nozzleleakage will be avoided. Partial cavitation will also be avoided. Sincethe line is always lled with fuel, sudden changes in pump delivery willnot result in troublesome irregularities in 'the engine torque curve.

I claim as my invention:

1. A check valve for controlling the supply of liquid fuel from ajerk-type pump into a. fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a reciprocable valvemember normally urged by spring pressure into engagement with said seatand being adapted to lift in response to a predetermined pressure insaid inlet passage and to close upon relief of said pressure, adifferential dashpot chamber, a differential piston disposed in saidchamber and movable with said valve member in response to said springpressure, opposite ends of said piston having peripheral clearances withsaid chamber to provide restricted inlet and egress orifices open tosaid outlet passage, said piston acting to maintain fuel in said chamberunder pressure during the closing movement of said valve member.

2. A check valve for controlling the supply of fuel from a jerk-typepump into a fuel injection line, said valve comprising, in combination,a body, a stationary valve member in said body and having an inletpassage with a valve seat, an axial sleeve on said valve member formedwith a differential bore having pilot guides of different diameters atopposite ends, a retainer threaded into said body to confine said valvemember in position and having an axial bore loosely en-` circling said`sleeve and communicating withan outlet passage, said sleeve havingradial ports opening from Ithe inner end of said rst mentioned bore toan annular passage defined between said sleeve and said retainer, adifferenital plunger reciprocable in said differential -bore and havinga valve member on one end adapted for engagement with said seat, pistonson opposite ends of said plunger and reciprocable -in said pilot guidesand defining therewith intermediate clearances constituting restrictedinlet and egress orifices, said differential bore intermediatesaidpistons constituting a dashpot chamber, and spring means acting onthe large end of said plunger in a direction to close said valve memberagainst the resistance of the pressure-induced in said chamber.

3. A check valve for controlling vthe supplyof fuel from a jerk-typepump into a fuel injection line, said valve comprising, in combination,a body, a stationary valve member in said body and having an inletpassage with a valve seat and formed with a differential bore havingpilot guides of different diameters at opposite ends, a housing havingan axial bore loosely encircling said stationary valve member andcommunicating with an outlet passage, said stationary valve memberhaving radial ports opening from the inner end of said first mentionedbore to an annular passage defined between said stationary valve memberand said housing, a differential plunger reciprocable in saiddifferential bore and having a valve member on one end adapted forengagement with said seat, pistons onv opposite ends of said plunger andreciprocable in said pilot guides and defining therewith intermediateclear-v ances constituting restricted inlet and egress orices, saiddifferential bore intermediate said pistons constituting a dashpotchamber, and spring means acting on said plunger in a direction to closesaid valve member against the resistance of the pressure induced in saidchamber.

4. A check valve for controlling the supply of liquid fuel from ajerk-type pump through a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a passageway in saidmember providing communication between said inlet and outlet passages, adashpot chamber located within said stationary valve member at theoutlet side of said valve seat and opening at opposite ends respectivelyto said passageway, a dashpot piston reciprocable in said chamber, avalve member movable with said piston and adapted for engagement withsaid valve seat, and spring means normally urging said valve membertoward said valve seat, the opposite ends of said piston respectivelypresenting unequal pressure areas and coacting with the opposite ends ofsaid chamber to define inlet and egress openings.

5. A check valve for controlling 'the supply of liquid fuel from ajerk-type pump through a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a passageway in saidmember providing communication -between said inlet and outlet passages,a dashpot chamber located within said stationary valve member at thevoutlet side of said valve seat and opening at opposite endsrespectively to said passageway, a dashpot piston reciprocable in saidchamber, a valve member movable with said piston and adapted forengagement with said valve seat, and spring means normally urging saidvalvek member toward said valve seat, the opposite ends of said pistonrespectively presenting unequal pressure areas and coacting with theopposite ends' of said chamber to define inlet and egress openings, saidpassageway having a restricted flow area at a pointbetween said oppositeends of said chamber.

6. A check valve for controlling the supply of liquid fuel from ajerk-type pump through a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve'seat adapted for. connection to said pump and having anoutlet passage adapted for connection to said line, means defining adinerential dashpot cylinder having a large end and a small end openinginto said outlet passage, a differential plunger in said cylinder andhaving relatively large and small pistons on opposite ends thereofreciprocably disposed respectively in the large and small ends of saidcylinder, the space' within said cylinder between said pistons defininga dashpot chamber opening to said outlet passage to permit 'therestricted inlet and egress of fluid, a valve member movable with saidpiston and adapted for engagement `with said' valve seat, and springmeans acting on said plunger for normallyY urging said valve membertoward and into engagement with said valve seat, said large piston inresponse to the pressure in said outlet passage tending to move intosaidcylinder in opposition to the pressure in said outlet passage actingon said small piston in the closing movement of said valve member. i

7. A check valve for controlling the supply of liquid fuel from ajerk-type pump into a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet ,passage with anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a reciprocable valvemember in said outlet passage normally urged by spring pressure intoengagement with said seat and being adapted to lift in response to apredetermined pressure in said inlet passage and to close upon relief ofsaid pressure, a differential dashpot chamber fixed in said outletpassage and having restricted communication with said outlet passage forthe inlet and egress to and from said chamber of fuel respectively inthe opening and closing movements of said valve member, and adiierential piston disposed for reciprocation in said chamber andmovable with said valve member, the opposite ends of said pistonpresenting external and face areas of unequal size exposed at spacedpoints to the pressure in said outlet passage, and the large end of saidpiston being movable into said chamber to expel fluid therefrom duringthe closing movement of said valve member, whereby to retard saidmovement.

8. A check valve for controlling the supply of liquid fuel fromavjerk-type pump into a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve seat adapted for connectionto said pump and having anoutlet passage adapted for connection to said line, a reciprocable valvemember in said outlet passage normally urged by spring pressure intoengagement with said seat and being adapted to lift in response to apredetermined pressure in said inlet passage and to close upon relief ofsaid pressure, a differential dashpot chamber fixed in said outletpassage and having restricted communication with said outlet passage forthe inlet and egress to and from said chamber of fuel respectively inthe opening and closing movements of said valve member, and adifferential piston disposed for reciprocation in said chamber andmovable with said valve member, the oppositeends of said pistonpresenting external end face areas of unequal size exposed at spacedpoints to the pressure in said outlet passage, said outlet passageintermediate said spaced points being restricted to effect a pressuredrop upon the flow of fuel therethrough, and the large end of saidpiston being movable into said chamber to expel fluid therefrom duringthe closing movement of said valve member, whereby to retard saidmovement.

9. A check valve for controlling the supply of liquid fuel from ajerk-type pump into a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage With anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a reciprocable valvemember in said outlet passage normally urged by spring pressure intoengagement with said seat and being adapted to lift in response to apredetermined pressure in said inlet passage and to close upon relief ofsaid pressure, a differential dashpot chamber fixed in said outletpassage and having restricted communication with said outlet passage forthe inlet and egress to and from said chamber of fuel respectively inthe opening and closing movements of said valve member, and adifferential piston disposed forv reciprocation in said chamber andmovable with said valve member, with the small end of said pistonlocated adjacent said valve seat and the large end of said pistonlocated remote from said valve seat, the opposite ends of said pistonpresenting external end face areas of unequal size exposed at spacedpoints to the pressure in said outlet passage, and the large end of saidpiston being movable into said chamber to expel fluid therefrom duringthe closing movement of said valve member, whereby to retard saidmovement.

l0. A check valve for controlling the supply of liquid fuel from ajerk-type pump into a fuel injection line, said valve comprising, incombination, a stationary valve member having an inlet passage with anannular valve seat adapted for connection to said pump and having anoutlet passage adapted for connection to said line, a reciprocable valvemember normally urged by spring pressure into engagement with said seatand being adapted to lift in response to a predetermined pressure insaid inlet passage and to close upon relief of said pressure, adifferential dashpot chamber, a differential piston disposed in saidchamber and movable with said valve member in response to saidspringpressure with the small end of said piston located adjacent said valveseat and the large end of said piston located remote from said valveseat, opposite ends of said piston having peripheral clearances withsaid chamber to provide restricted inlet and egress orices located atspaced points to said outlet passage, the clearance about said small endof said piston being more restricted than the clearance about said largeend of said piston, said outlet; passage intermediate said spaced pointsbeing restricted to effect a pressure drop upon the flow of fueltherethrough, said piston acting to maintain fuel in said chamber underpressure during the closing movement of said valve member.

JAMES F. HOFFER.

